Progress Test 5

Question 1

What is a parcel of air?

Answer 1

Term used to distinguish between bits of air that have different characteristics
-bubbles or balloons of air

Question 2

What is Humidity?

Answer 2

The measure of how much water vapour content contained in a parcel of air
-This is largely responsible for the weather

Question 3

What is the effect of water vapour on the humidity?

Answer 3

The more water vapour content in a parcel of air the more humid it is.

Question 4

What is Absolute Humidity?

Answer 4

The absolute humidity is the amount (weight) of water vapour the parcel of air contains.

Question 5

What effects the amount of water vapour a parcel of air can contain, what is the biggest effect and why?

Answer 5

This is dependent of pressure and temperature, but the biggest impact is the temperature as warmer air can contain more water vapour content than cooler air at the same pressure.

Question 6

Is the relationship between temperature and Humidity linear or non linear?

Answer 6

Non-linear (not directly comparable).

Question 7

How much water vapour can a parcel of air contain at 10, 20 and 30 degrees Celcius?

Answer 7

10 = 9 grams H20 per cubic meter of air
20 = 17 grams H20 per cubic meter of air
30 = 30 grams H20 per cubic meter of air

Question 8

How is humidity (water vapour carrying content) measured?

Answer 8

In Percentage.

Question 9

What does saturated humidity mean?

Answer 9

Means there is 100 percent humidity and the parcel of air has no more room for water vapour.

Question 10

What will happen to the relative humidity is the parcel of air is cooled, and what happen when relative humidity is cooled at 100%?

Answer 10

The relative humidity will increase, any further cooling will result in the water vapour condensing into visible droplets (rain, cloud, mist)

Question 11

What is dew point?

Answer 11

The temperature of which 100% humidity occurs.

Question 12

What will happen when a parcel of air has more water vapour content than the surrounding atmosphere?

Answer 12

It will tend to rise as water vapour less dense and will rise quicker than the surrounding air.

Question 13

What will a rise of air effect the temperature?

Answer 13

Due to being less dense the rise of air will decrease in temperature due to the average lapse rate. This will decrease the amount of water vapour the air can hold.

Question 14

What is the environmental lapse rate and what is used to measure?

Answer 14

The environmental lapse rate is the real atmosphere on a given day in a given place.
This is measured by Radiosonde balloons

Question 15

Describe the Dry Adiabatic Lapse rate.

Answer 15

The temperature lapse rate of dry air (air without water vapour content). The lapse rate always remains the same as the composition of gases remains constant.

Question 16

What is the Dry Adiabatic lapse rate?

Answer 16

DALR is -3 degrees per 1000ft.

Question 17

Describe the Saturated Adiabatic Lapse rate.

Answer 17

Temperature lapse rate of saturated air (air at 100% humidity). The lapse rate remains constant as the composition of gases remains constant.

Question 18

What is the Saturated Adiabatic Lapse rate?

Answer 18

SALR is -1.5 degrees per 1000ft.

Question 19

What gives off energy, Liquid to a gas or gas to a Liquid?

Answer 19

Gas to a liquid.

Question 20

What is the Adiabatic Process?

Answer 20

The process of heat exchange with no gain or loss within the system.

Question 21

What is the process of a gas turning to a Liquid called?

Answer 21

Condensation

Question 22

How can condensation effect the adiabatic lapse rate?

Answer 22

The release of energy slows down the cooling as the parcel of air rises and therefore reduces the adiabatic lapse rate.

Question 23

What is the adiabatic lapse rate?

Answer 23

The rate of which the temperature of a parcel of air decreases with altitude as it ascends.

Question 24

What is the Environmental lapse rate?

Answer 24

The way the parcel of air behaves depending on how the adiabatic lapse rate compares with the temperature lapse rate of the general environment.

Question 25

True or False? There is a standard environmental lapse rate which is named the international standard atmosphere ELR.

Answer 25

False. There is no standard environment lapse rate. However there is a defined ISA ELR of -1.98 degrees every 1000ft which caters for an average relative humidity.

Question 26

What is Absolute instability?

Answer 26

-This occurs when the ELR is less than the DALR. - The parcel of air cools at a lesser rate than the surround atmosphere -During it's ascent it's temperature relative to the surroundings increases. -The parcel of air does not resist the vertical motion and accelerates vertically.

Question 27

What is absolute stability?

Answer 27

-If the ELR is greater than the SALR. - The parcel of air would not rise very far as it's temperature would quickly become lower than the surrounding atmosphere and will sink again. -The parcel of air resists vertical motion.

Question 28

What is conditional instability?

Answer 28

-If the ELR is between the DALR and the SALR. -The parcel of air cools at a similar rate to the ELR since it is partially saturated and requires external influence to make it rise. --When it reaches the dew point it's lapse rate changes to SALR. -As the Parcel of air ascends with a SALR it becomes increasingly warmer than it's surroundings which results in an accelerated ascent.

Question 29

What is Adiabatic Warming?

Answer 29

When the parcel of air descends it warms at the atmospheric lapse rate (depending on the humidity) -e.g., the non-winward side of a mountain becomes warmer.

Question 30

Name four effects of atmospheric instability.

Answer 30

1. occurs by atmospheric heating from below 2. results in air moving vertically upwards 3.Results in Cumulous or heaped clouds 4. Creates more turbulence, Rain shower and better visibility.

Question 31

What are four effects of atmospheric stability?

Answer 31

1. Usually occurs by atmospheric cooling from below. 2. Results in some vertical movement but limited to the lower layers 3. Stratus or layer type clouds covering large areas 4. Smooth conditions, precipitation that can last a long time and visibility is poor.

Question 32

Why is /M00 as a measure of dew point on the TAF between -0.0 and -0.4?

Answer 32

This is because temperature and dew point in expressed in whole numbers so M-0.0 could be anything from that number to -0.4. M01 would be anything from -0.5 to -1.4.

Question 33

How is relative humidity normally expressed?

Answer 33

This is usually expressed as a percentage of the amount of water vapour in the atmosphere compared to the maximum amount of water vapour in the atmosphere.